Six fire engines and around 40 firefighters tackled a fire on Faraday Road in Wimbledon.
Two adjoining sheds were destroyed by the fire. A man was treated on scene by London Ambulance Service crews.
Firefighters cooled a gas cylinder to an ambient temperature as a precaution, as some cylinders can explode when exposed to heat.
A 50-metre cordon was in place and the road was closed at the junction of Faraday Road and Trinity Road while firefighters make the scene safe. Drivers were advised to find alternative routes.
The fire is believed to have been accidental and caused by hot works taking place.
The Brigade’s 999 Control Officers took 11 calls to the fire.
The Brigade was called at 1420 and the fire was under control by 1633. Fire crews from Wimbledon, Wandsworth, Mitcham and surrounding fire stations attended the scene.